Automatic sprinkler heads generally have a body with a passageway for a fire extinguishing fluid, such as water, which is sealed off by a closure assembly. The closure assembly is sometimes referred to as a "valve" or "valve assembly." Opposite the passageway, a deflector plate is typically affixed to a frame extending from the body of the sprinkler head. Between the closure assembly and the deflector plate, there usually is placed a heat-sensitive trigger element, such as a fluid-filled glass bulb or a heat-fused soldered link. At normal room temperatures, the trigger element maintains the closure assembly closed. The trigger element is designed to break, fracture or disintegrate, at selected elevated temperatures. When the trigger element breaks, the external pressure which keeps the closure assembly closed is removed, and the pressure of the water in the sprinkler head supply line normally forces the closure assembly, any mounting and holding means for the trigger element, and any components or fragments of the trigger element clear of the region between the passageway and the deflector plate.
When the closure assembly is forced open upon triggering, a problem may arise if the closure assembly or a portion of the trigger element becomes lodged against the deflector plate and/or sprinkler frame by the water rushing out of the passageway. Any lodgement can impair the flow of water from the sprinkler head, thereby reducing the fire-extinguishing capability of the sprinkler system.